1. Into a mixing bowl, put flour and butter then rub together using fingertips until mixture resembles breadcrumbs. Add caster sugar and bring together using hands.

2. Dust work surface with flour and turn out dough on to worksurface. Form into a thick sausage shape. Wrap in cling film and chill for 30min.

3. Slice dough widthways, into roughly 1cm (½in) thick discs and remove cling film. Line a baking sheet with baking parchment, and put shortbread discs on sheet with plenty of space between to allow them to spread when cooking. Sprinkle with demerara or granulated sugar.

4. Bake at 200°C (180°C fan) mark 6 for 15-16min, until pale golden. Cool for 10min on baking sheet before transferring to a wire rack to cool completely. Store in an airtight container for up to one week.